The present invention relates to high speed centrifuge rotor including a rotor head and demountable swinging buckets.
Centrifuge rotors of the swinging bucket type typically include a rotor head from which is suspended a plurality of buckets containing the liquid to be centrifuged. The buckets are supported by hangers which enable the buckets to pivot about their mounting axes. When the rotor is stopped, the buckets hang vertically downward under the influence of gravity. When the rotor is spinning, the buckets swing outward in response to centrifugal force.
In a number of prior designs, the hanger incorporates some means to enable limited radial movement of the bucket when the rotor is spinning. The bucket is thereby able to engage a portion of the rotor to gain support against the centrifugal force which is acting on it. Thus, by transferring the load to the rotor, the hanger is relived of having to carry the high G force being exerted on the bucket. In many of these previous designs it has been common to mount the bucket to the rotor from the underside of the rotor. This has the disadvantage that the operator cannot easily view the mounting operation and might mount the bucket incorrectly. As a result, during operation the bucket may not pivot as intended and may become detached from the rotor.
An approach which differed from earlier rotor designs was provided by Michael J. Scanlon in U.S. Pat. No. 3,687,359, issued Aug. 29, 1972. Scanlon disclosed a rotor having cavities which were open to the top of the rotor. This enabled buckets to be mounted in the rotor from the top side. The bucket is provided with a spherical flange which seats in a spherical portion of the cavity. When the rotor is spun, the flanged portion of the bucket pivots in its spherical seat, allowing the bucket to swing from a vertical to a horizontal position. It has been observed that in so-called "ball and socket" designs of this type, there is some tendency for the bucket to stick in the transition between the horizontal and vertical positions. A malfunction of this kind is, of course, likely to have a detrimental effect on the separation process. It has been determined that the sticking problem results from non-uniform friction between the sliding surfaces of the "ball and socket" parts of the bucket and rotor. In view of the relatively large contact area involved, the presence of excessive friction is not altogether surprising.
It will be seen, therefore, that there is a need for an improved centrifuge rotor in which the buckets are mountable from the top side of the rotor and in which the bucket mountings function reliably.